Soil samplers such as cone penetrometers have been used throughout the world by engineers to measure soil properties. Part of the testing regime utilizes soil sampling to help determine mechanical properties at various depths and locations. This data is used for many types of pre- and post-construction evaluation. Other uses for sampling are in the environmental area for monitoring and remediation. Soil sampling is a key diagnostic technology used to demonstrate compliance with the environmental laws.
Many samples, due to the nature of the field conditions, have to be taken in a horizontal position. This would include samples underneath existing structures, such as tanks or other industrial equipment or buildings.
Prior art samplers, such as that shown in FIG. 1 of this application, used a ball and detent latch system, which used gravity to set steel balls in a grooved shaft. The principle of operation was that the balls were to lock the shaft in position to allow the sampler to be pushed forward to obtain a core soil sample. This type of sampler was designed to be pushed vertically into the ground, with the center rod in the forward position. The rod would then be retracted when the sampler reached the target, causing the steel balls to lock and enable the body to be pushed forward to collect the sample. This prior art design had several operating drawbacks, such as premature lock-up, incomplete latching, as well as not being able to operate in a position that was significantly off the vertical position. The problem with the prior design was that retraction of the central shaft was not always a uniform movement and could include some forward motion during the retraction step. With the design as shown in FIG. 1, any forward motion, even to a slight degree, during the retraction step could jam the balls, causing the balls to break or to break the exterior housing or the central shaft when the balls jammed in the tapered housing in which they were stored. Sometimes the balls would not fully latch into the groove, which would cause problems in obtaining the sample, such as sample loss prior to withdrawal of the sampler. The mislatching was primarily due to radial point loads on the latching piece body transmitted through the balls, which caused failure of the body and damage to the cone rod surface.
To address these shortcomings of the prior design, the apparatus and method of the present invention were developed to provide a distributed load-bearing surface with forces preferably in the axial direction. The layout of components is such that positive latching occurs in any orientation. The present invention allows back and forth movement of the rod up until the point of latching without damage to any of the parts. The new design can be accomplished within the dimensions of the old design while retaining its mechanical strength features. Apart from the prior design as shown in FIG. 1, other designs of samplers have been used in the past, as indicated in U.S. Pat. Nos. 5,125,266 and 5,127,261. In this design the sample tube extends out of a housing and into the formation in order to grab the sample.